1,4-Phenylene diallyl bis(carbonate)

The title compound represents the first instance of a 1,4-phenylene bis(carbonate) derivative characterized by X-ray diffraction.

The title molecule, C 14 H 14 O 6 , is based on a benzene core di-substituted by allyl carbonate groups in the para positions. The molecule is placed on an inversion centre, and the substituents are twisted with respect to the central benzene ring plane. The crystal structure does not include significant intermolecular interactions other than weak C-HÁ Á ÁO contacts between CH groups in the benzene ring and carbonate O atoms.
The reaction between allyl chloroformate (ACF) and a diol affords mono allyl carbonate and diallyl carbonate derivatives. The reaction of ACF with hydroquinone gives allyl-4-hydroxyphenyl carbonate (Flores et al., 2009) and 1,4-phenylene diallyl bis(carbonate). Herein, we report the structure of the latter. The title compound represents the first instance of a 1,4-phenylene bis(carbonate) derivative to be characterized by X-ray diffraction.

data reports
The molecule lies on an inversion centre in space group P2 1 /n, with the symmetry element coinciding with the centre of the benzene ring ( Fig. 1). This ring is disubstituted in the para positions by allyl carbonate groups, which are not coplanar with the ring: the dihedral angle between the mean plane of the benzene and the plane of the carbonate group O4/ C5/O6/O7 is 68.69 (4) , and the dihedral angle between the carbonate group and the allyl group C8/C9/C10 is 51.1 (2) . This twisted conformation was previously observed for the four reported X-ray structures bearing a benzene ring substituted by an allyl carbonate group (Flores Ahuactzin et al., 2009;Herrera-Gonzá lez et al., 2009;Li et al., 2019;Schmid et al., 2019). This conformation does not promote strong intermolecular contacts in the crystal structure, as hydrogen bonds orinteractions. The benzene H atoms are, however, engaged in C-HÁ Á ÁO contacts with neighbouring molecules. The C1-H1 group makes an almost linear contact with the carbonate O atom O7 (

Synthesis and crystallization
To a three-neck round-bottom flask connected to an addition funnel, hydroquinone (2.28 g, 20.7 mmol) was added and dissolved in 20 ml of THF under an argon atmosphere. After continuous agitation, a homogeneous phase was observed in the reaction flask, and NaHCO 3 (0.86 g, 10.3 mmol), previously dissolved in 5 ml of distilled water, was added. Then, the reaction flask was placed in an ice bath and allyl chloroformate (1.09 ml, 10.3 mmol) was slowly added dropwise, maintaining the agitation. After complete addition, the reaction was left for 5-10 minutes at 273 K, and then at room temperature for 2 h. After completion of the reaction, the products were extracted in a separation funnel using CH 2 Cl 2 , and dried over anhydrous Na 2 SO 4 . The reaction mixture was filtered and concentrated. The resulting concentrated solution was precipitated into hexane. The precipitate was collected, washed with hexane, and dried in vacuo (yield: 1.152 g, 20%). Transparent prismatic single crystals were recovered from this material for X-ray study (see Fig. 1

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

Figure 1
Molecular structure of the title compound. Non-H atoms are drawn at the 30% probability level. Non-labelled atoms are generated by the symmetry operation 1 À x, 1 À y, Àz. The inset is the raw material as obtained from the synthesis. The edges of the hexagonal flake have dimensions of ca 5 mm. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x À 1 2 ; Ày þ 1 2 ; z À 1 2 ; (ii) x; y À 1; z.

Figure 2
Part of the crystal structure based on C1-H1Á Á ÁO7 interactions (Table 1, entry 1). The asymmetric unit is coloured in grey, while orange, green and magenta moieties are generated by inversion, 2 1 axis and n glide plane, respectively.

Figure 3
Part of the crystal structure based on C2-H2Á Á ÁO6 interactions (